The proposed project adapts the prototype approach (developed by Rosch for the study of object categorization and subsequently applied by Cantor, Mischel, Horowitz and others to social categorization) to the domain of human emotion. It is argued that this approach can help resolve some classic problems in emotion theory and research--regarding, e.g., the nature and number of "basic" emotions, the overall structure of the emotion domain, and the content and internal organization of discrete emotional experiences. The prototype approach hypothesizes that categories of emotional experience are "fuzzy sets" organized around prototypical examples. These categories can be divided into several hierarchical "levels" varying in inclusiveness. One level (including familiar categories such as anger, fear, sadness, and happiness) can be identified as the "basic level" of the emotion hierarchy because it contains the most useful, informative distinctions for most everyday purposes. In Study 1, subjects will sort emotion terms into categories and suggest names for these categories. These sortings will be submitted to hierarchical clustering analysis, producing a representation of the hierarchical organization of the emotion domain. This cluster analysis, along with analysis of the names provided by subjects for sorted categories, will identify the hierarchy's "basic level". In Study 2, subjects will provide accounts of (either real or "typical") experiences corresponding to each basic emotion category identified in Study 1. The most frequent features used to describe a given emotion will be determined. A new sample of subjects will judge each pair of features in terms of their similarity and relatedness. These judgments will be submitted to hierarchical cluster analysis in order to produce a "picture" of the prototype for that emotion category--representing its typical antecedent conditions, verbal and nonverbal responses, and self-control processes. Several additional studies, described more briefly, will begin to demonstrate the influence of the emotion domain's hierarchical organization and category prototypes on the cognitive processing of emotional information. The potential contributions of these studies to understanding normal and abnormal emotional development, clinical syndromes involving atypical emotional experiences, and cross-cultural similarities and differences in emotional experience are discussed.